Organophosphorus-catalyzed relay oxidation of H-Bpin: electrophilic C-H borylation of heteroarenes.

A nontrigonal phosphorus triamide (, P{N[-NMe-CH]}) is shown to catalyze C-H borylation of electron-rich heteroarenes with pinacolborane (HBpin) in the presence of a mild chloroalkane reagent. C-H borylation proceeds for a range of electron-rich heterocycles including pyrroles, indoles, and thiophenes of varied substitution. Mechanistic studies implicate an initial P-N cooperative activation of HBpin by to give -hydrido diazaphospholene , which is diverted by Atherton-Todd oxidation with chloroalkane to generate -chloro diazaphospholene . DFT calculations suggest subsequent oxidation of pinacolborane by generates chloropinacolborane (ClBpin) as a transient electrophilic borylating species, consistent with observed substituent effects and regiochemical outcomes. These results illustrate the targeted diversion of established reaction pathways in organophosphorus catalysis to enable a new mode of main group-catalyzed C-H borylation.